The disclosure relates to manufacture of materials used for enhanced abradable coatings for a gas turbine engine.
In compressor and turbine sections of a gas turbine engine, air seals are used to seal the interface between a rotating structure, such as a hub or a blade, and a fixed structure, such as a housing or a stator. For example, typically, circumferentially arranged blade seal segments are fastened to a housing, for example, to provide the seal.
Relatively rotating components of a gas turbine engine are not at all times perfectly cylindrical or coaxial with one another during engine operation. As a result, the relatively rotating components may occasionally rub against one another. To this end, an abradable material typically is adhered to the blade seal segments or full rings and/or the rotating component.
Abradable seals in the compressor section of gas turbine engines include characteristics such as, good abradability, spall resistance, and erosion resistance. Abradable seals are required to exhibit a smooth surface, low gas permeability, and environmental durability. The seal is a sacrificial element in order to minimize blade wear, so it is abradable. The seal must also minimize gas flow leakage through the seal, so a low gas permeability is desirable.
Abradable coatings for the seals are always a compromise between abradability and erosion resistance. In order to maintain blade tip clearances over time, the seal material needs to be tough and resistant to erosion. Conventional seal materials tend to be soft and weak in order to have good abradability. Recently, MAXMETs (MAX phase reinforced metal matrix composites) have shown tremendous promise as next generation compressor abradable coatings.
MAXMET composite coatings processed by powder metallurgy routes and thermal spraying techniques have showed excellent promise due to increased erosion resistance, and significant reduction in coefficient of friction by incorporation of up to 50 vol. % MAX phases into current abradable systems. The wear response of the newly developed coatings have also showed significant changes in the rub mechanism. However, to scale up, methods of manufacture and processing parameters for enabling MAXMET applications as low and high temperature Low Pressure Compressor and High Pressure Compressor abradable coatings is currently under development. One of the challenges during use of thermal spraying methods to create abradable coatings is oxidation and low flow behavior of MAX phase particles.